netdev - [PATCH] net: ethtool: not call vzalloc for zero sized memory request

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Message-Id: <1553752869-10312-1-git-send-email-lirongqing@baidu.com>
Date:   Thu, 28 Mar 2019 14:01:09 +0800
From:   Li RongQing <lirongqing@...du.com>
To:     netdev@...r.kernel.org
Subject: [PATCH] net: ethtool: not call vzalloc for zero sized memory request

NULL or ZERO_SIZE_PTR will be returned for zero sized memory
request, and derefencing them will lead to a segfault

so it is unnecessory to call vzalloc for zero sized memory
request and not call __ethtool_get_strings which always uses
the allocated memory

this also fixes a possible memory leak if phy_ethtool_get_stats
returns error, memory should be freed before exit

Signed-off-by: Li RongQing <lirongqing@...du.com>
Reviewed-by: Wang Li <wangli39@...du.com>
---
 net/core/ethtool.c | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index b1eb32419732..3e971a36e37c 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -1797,11 +1797,16 @@ static int ethtool_get_strings(struct net_device *dev, void __user *useraddr)
 	WARN_ON_ONCE(!ret);
 
 	gstrings.len = ret;
-	data = vzalloc(array_size(gstrings.len, ETH_GSTRING_LEN));
-	if (gstrings.len && !data)
-		return -ENOMEM;
 
-	__ethtool_get_strings(dev, gstrings.string_set, data);
+	if (gstrings.len) {
+		data = vzalloc(array_size(gstrings.len, ETH_GSTRING_LEN));
+		if (!data)
+			return -ENOMEM;
+
+		__ethtool_get_strings(dev, gstrings.string_set, data);
+	} else {
+		data = NULL;
+	}
 
 	ret = -EFAULT;
 	if (copy_to_user(useraddr, &gstrings, sizeof(gstrings)))
@@ -1897,9 +1902,14 @@ static int ethtool_get_stats(struct net_device *dev, void __user *useraddr)
 		return -EFAULT;
 
 	stats.n_stats = n_stats;
-	data = vzalloc(array_size(n_stats, sizeof(u64)));
-	if (n_stats && !data)
-		return -ENOMEM;
+
+	if (n_stats) {
+		data = vzalloc(array_size(n_stats, sizeof(u64)));
+		if (!data)
+			return -ENOMEM;
+	} else {
+		data = NULL;
+	}
 
 	ops->get_ethtool_stats(dev, &stats, data);
 
@@ -1941,14 +1951,19 @@ static int ethtool_get_phy_stats(struct net_device *dev, void __user *useraddr)
 		return -EFAULT;
 
 	stats.n_stats = n_stats;
-	data = vzalloc(array_size(n_stats, sizeof(u64)));
-	if (n_stats && !data)
-		return -ENOMEM;
+
+	if (n_stats) {
+		data = vzalloc(array_size(n_stats, sizeof(u64)));
+		if (!data)
+			return -ENOMEM;
+	} else {
+		data = NULL;
+	}
 
 	if (dev->phydev && !ops->get_ethtool_phy_stats) {
 		ret = phy_ethtool_get_stats(dev->phydev, &stats, data);
 		if (ret < 0)
-			return ret;
+			goto out;
 	} else {
 		ops->get_ethtool_phy_stats(dev, &stats, data);
 	}
-- 
2.16.2